Canadian Military Leak to Russia Riles Allies

By

Alistair MacDonald in Toronto and

Siobhan Gorman in Washington

Updated March 28, 2012 3:56 p.m. ET

A Canadian naval officer allegedly leaked a large cache of military communications data to Russia, causing a serious breach between U.S. and Canadian intelligence officials, said people familiar with the situation.

Though U.S. and Canadian officials have now patched up their differences, the fallout underscored the seriousness with which Washington has taken the incident despite Canadian insistence that allies haven't been overly...